1. Field of the Invention
The present invention relates to a differential amplifier circuit, and more specifically, to a high slew rate differential amplifier circuit.
2. Description of the Related Art
A conventional differential amplifier circuit is described. FIG. 3 is a circuit diagram illustrating the conventional differential amplifier circuit.
A slew rate control circuit 91 includes two differential pairs (not shown) and a current mirror circuit (not shown), and monitors an input voltage Vinp and an input voltage Vinn. The slew rate control circuit 91 does not supply an output current when a differential voltage between the input voltage Vinp and the input voltage Vinn is lower than 0.5 V, and starts to supply the current gradually when the differential voltage is 0.5 V or higher. Then, when the differential voltage between the input voltage Vinp and the input voltage Vinn is 0.9 V or higher, the slew rate control circuit 91 supplies a constant current. Therefore, when the input voltage difference is large, the differential amplifier circuit is driven with the currents supplied from both the slew rate control circuit 91 and a current source 92 so as to increase a slew rate of an output voltage Vout (see, for example, Japanese Patent Application Laid-open No. Hei 06-112737).
In the conventional technology, however, the slew rate control circuit 91 having a complicated circuit configuration is provided and accordingly the differential amplifier circuit is increased in circuit size.